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JEE Mains · Maths · STD 12 - 3 and 4 . metrices and determinant

ધારોકે \(P =\left[\begin{array}{ccc}3 & -1 & -2 \\ 2 & 0 & \alpha \\ 3 & -5 & 0\end{array}\right],\) જ્યાં \(\alpha \in R .\) ધારોકે શ્રેણિક \(Q =\left[ q _{ ij }\right]\) એ કોઈક શૂન્યતર \(k \in R\) માટે \(PQ = kI _{3}\) નું, સમાધાન કરે છે. તો \(q _{23}=-\frac{ k }{8}\) અને \(|Q|=\frac{k^{2}}{2}\) હોય, તો \(\alpha^{2}+k^{2}=.........\)

  1. A \(17\)
  2. B \(21\)
  3. C \(13\)
  4. D \(19\)
Verified Solution

Answer & Solution

Correct Answer

(A) \(17\)

Step-by-step Solution

Detailed explanation

\(PQ = kI\) \(| P | \cdot| Q |= k ^{3}\) \(\Rightarrow| P |=2 k \neq 0 \Rightarrow P\) is an invertible matrix \(\because PQ = kI\) \(\therefore Q=k P^{-1} I\) \(\therefore Q=\frac{\text { adj.P }}{2}\) \(\because q _{23}=-\frac{ k }{8}\)…
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